A Transporter Interactome Is Essential for the Acquisition of Antimicrobial Resistance to Antibiotics

Abstract

Awareness of the problem of antimicrobial resistance (AMR) has escalated and drug-resistant infections are named among the most urgent problems facing clinicians today. Our experiments here identify a transporter interactome and portray its essential function in acquisition of antimicrobial resistance. By exposing E. coli cells to consecutive increasing concentrations of the fluoroquinolone norfloxacin we generated in the laboratory highly resistant strains that carry multiple mutations, most of them identical to those identified in clinical isolates. With this experimental paradigm, we show that the MDTs function in a coordinated mode to provide an essential first-line defense mechanism, preventing the drug reaching lethal concentrations, until a number of stable efficient alterations occur that allow survival. Single-component efflux transporters remove the toxic compounds from the cytoplasm to the periplasmic space where TolC-dependent transporters expel them from the cell. We postulate a close interaction between the two types of transporters to prevent rapid leak of the hydrophobic substrates back into the cell. The findings change the prevalent concept that in Gram-negative bacteria a single multidrug transporter, AcrAB-TolC type, is responsible for the resistance. The concept of a functional interactome, the process of identification of its members, the elucidation of the nature of the interactions and its role in cell physiology will change the existing paradigms in the field. We anticipate that our work will have an impact on the present strategy searching for inhibitors of AcrAB-TolC as adjuvants of existing antibiotics and provide novel targets for this urgent undertaking.

Efflux drug transporters at the forefront of antimicrobial resistance

“…Taking this a step further, this network of efflux transporters is not only helping to protect against antimicrobials but is in fact the first line of defense of bacteria against a toxic chemical attack (Shuster et al 2016 ). Without efflux transporters, the quickest bacterial response would be to switch on the production of genes that actively destroy or disable the chemical threat.…”

Multidrug efflux pumps and their role in antibiotic and antiseptic resistance: a pharmacodynamic perspective

“…These three proteins ensure the substrate capture from the outer leaflet of the inner membrane bilayer or the periplasmic space and, the substrate transport across the periplasm and the outer membrane to the external medium receiving energy from the proton motive force [10,44]. The three-dimensional structure of the most documented RND pump AcrB of E. coli comprising 12 transmembrane helices was first described as a homotrimeric symmetrical protein [45].…”

Synergy between Active Efflux and Outer Membrane Diffusion Defines Rules of Antibiotic Permeation into Gram-Negative Bacteria

“…Two types of efflux pumps operate and affect drug concentrations in different bacterial cell compartments ( 14 ). Some efflux transporters transport drugs across the IM and affect cytoplasmic drug accumulation ( 15 , 16 ). Other transporters, such as those belonging to the r esistance- n odulation-cell d ivision (RND) superfamily, associate with additional proteins located in the periplasm and in the OM and function as transenvelope (across the two membranes) efflux pumps ( 17 ).…”